The invention relates to venous reservoirs used in closed circuits for the temporary storage of blood, and is particularly concerned with a soft shell reservoir basically formed by a pair of overlapping thermoplastic or heat weldable resinous sheets joined along weld lines to define both a blood storage chamber and ancillary support structure. A reservoir of this general type, and the environment of the invention, will be noted in U.S. Pat. No. 4,622,032, Katsura et al, issued Nov. 11, 1986.
As blood enters such reservoirs, air is often entrained therein. Thus, it is essential that provision be made to effectively remove such air or air bubbles before the blood is returned to the patient. To this end, the reservoirs incorporate air vents, normally in the nature of tubes sealed to the reservoir and communicating with a high point of the collection chamber. However, in soft shell reservoirs in particular, problems arise in effecting a complete debubbling or air removal. Such problems can result from various factors including an inadequate flow pattern for the blood within the storage chamber, or the particular construction of the reservoir and chamber itself. In this latter case, a significant problem with regard to soft shell reservoirs is the tendency for air bubbles to collect along the heat sealed seams and the inability to adequately move these air bubbles to the air vent or vents for discharge. Typical examples of high-frequency welds in soft shell bags will be noted in U.S. Pat. No. 4,507,123, Yoshida, Mar. 26, 1985; and U.S. Pat. No. 4,548,023, Danby et al, Oct. 22, 1985.